In the Standard Model, the top quark plays a unique role as the heaviest known fundamental particle and as a quark that decays before it is able to hadronize. Top quarks are expected to decay to a W-boson and a b-quark nearly 100% of the time. If the branching ratio of t → Wb is lower than one, the distribution of the number of b-tagged jets will shift to lower multiplicities. A simultaneous likelihood fit to the number of b-tagged jets distributions in the lepton+jets and dilepton channels is performed on 4.7 fb−1 of data collected by the ATLAS detector to extract both the branching ratio and the tt¯ cross section. The branching ratio of t → Wb, R, is measured to be 1.06±0.11, which is consistent with the Standard Model value. This is the first measurement of the t → Wb branching ratio performed with the ATLAS detector using both the lepton+jets and dilepton channels at the LHC. The tt¯ cross section is measured to be [special characters omitted] pb, which agrees with NNLO predictions.
|Commitee:||Arguin, Jean-Francois, Blazey, Gerald, Martin, Stephen|
|School:||Northern Illinois University|
|School Location:||United States -- Illinois|
|Source:||DAI-B 74/06(E), Dissertation Abstracts International|
|Keywords:||Branching ratio, Cross section, Dilepton final states, Large Hadron Collider, Pair production, Top quarks, W bosons|
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